U.S. patent application number 10/431336 was filed with the patent office on 2004-11-11 for disk drive system and method for operating same.
Invention is credited to Anostini, Luca, Ramaioli, Fabio, Salina, Alberto, Schenone, Alessandra, Ventura, Gianluca.
Application Number | 20040223251 10/431336 |
Document ID | / |
Family ID | 33416434 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040223251 |
Kind Code |
A1 |
Ventura, Gianluca ; et
al. |
November 11, 2004 |
Disk drive system and method for operating same
Abstract
A disk drive system is described which includes a disk having a
magnetic surface and a motor for rotating said disk, a magnetic
head being movable relative to said magnetic surface. The motor
generates a back electromotive force voltage having different
phases and the system comprising a plurality of switches for
switching said back electromotive force voltage, a control circuit
to control said plurality of switches to supply said back
electromotive force voltage to direct said head to a parking
position. The system also comprises a comparator adapted to compare
a single phase of the back electromotive force voltage with the sum
of the other phases of said back electromotive force voltage. The
comparator generates an output signal representative of the
comparation and the system comprises a logic block controlled by
the output signal of the comparator. The logic block is adapted to
determine time periods and a control sequence of the switches which
is associated to said time periods. The control sequence is
supplied to the control circuit so that the last generates control
signals to control said plurality of switches.
Inventors: |
Ventura, Gianluca; (Milano,
IT) ; Salina, Alberto; (Limibiate, IT) ;
Schenone, Alessandra; (Cisliano, IT) ; Ramaioli,
Fabio; (Melegnano, IT) ; Anostini, Luca;
(Corsico, IT) |
Correspondence
Address: |
HOGAN & HARTSON LLP
ONE TABOR CENTER, SUITE 1500
1200 SEVENTEENTH ST
DENVER
CO
80202
US
|
Family ID: |
33416434 |
Appl. No.: |
10/431336 |
Filed: |
May 7, 2003 |
Current U.S.
Class: |
360/75 ;
360/73.03; G9B/21.021; G9B/5.024; G9B/5.181; G9B/5.189 |
Current CPC
Class: |
G11B 2005/001 20130101;
G11B 21/12 20130101; G11B 5/54 20130101; G11B 5/012 20130101; G11B
5/553 20130101 |
Class at
Publication: |
360/075 ;
360/073.03 |
International
Class: |
G11B 021/02; G11B
015/46 |
Claims
1. (cancelled).
2. (cancelled).
3. (cancelled).
4. (cancelled).
5. (cancelled).
6. (cancelled).
7. (cancelled).
8. (cancelled).
9. (cancelled).
10. (cancelled).
11. A disk drive system comprising: a disk having a magnetic
surface; a motor for rotating said disk and for generating a back
electromotive force voltage having different phases; a magnetic
head being movable relative to said magnetic surface; a plurality
of switches for switching said back electromotive force voltage; a
control circuit to control said plurality of switches to supply
said back electromotive force voltage to direct said head to a
parking position; a comparator for comparing a single phase of the
back electromotive force voltage with the sum of other phases of
said back electromotive force voltage, and for generating an output
signal representative of the comparison; and a logic block
controlled by the output signal of the comparator for determining
time periods and for generating a control sequence associated with
said time periods, said control sequence being supplied to the
control circuit.
12. The system of claim 11, wherein said control sequence assures
the activation of the switches associated with phases of the back
electromotive force that have an absolute maximum value in one of
said time periods.
13. The system of claim 11, wherein said logic block further
comprises a counter for counting the time interval between a value
change and a successive value change of said output signal of the
comparator, and a time divider for dividing said time interval in
said time periods.
14. The system of claim 13, wherein said back electromotive force
comprises three phases, said time divider divides said time
interval in six time periods and said control sequence closes the
switches associated with two phases of the back electromotive force
that have an absolute maximum value, with respect to the other
phase in each one of said six time periods.
15. The system of claim 11, wherein said motor comprises a spindle
motor.
16. A method for operating a disk drive system including a disk
having a magnetic surface, a motor for rotating said disk, and a
magnetic head being movable relative to said magnetic surface, said
method comprising: generating a back electromotive force voltage
having different phases: switching said back electromotive force
voltage with a plurality of switches; controlling said plurality of
switches to supply said back electromotive force voltage to direct
said head to a parking position; comparing a single phase of the
back electromotive force voltage with the sum of other phases of
said back electromotive force voltage with a comparator;
determining time periods and a control sequence for the switches
associated with said time periods; and generating control signals
to control said plurality of switches according to said control
sequence.
17. The method of claim 16, wherein said control sequence assures
the activation of the switches associated with the phases of the
back electromotive force that have an absolute maximum value in one
of said time periods.
18. The method of claim 16, wherein determining time periods
comprises counting the time interval between a value change and a
successive value change of an output signal of the comparator, and
dividing said time interval in said time periods.
19. The method of claim 18, wherein said back electromotive force
comprises three phases, said time interval being divided into six
time periods and said control sequence closes the switches
associated to two phases of the back electromotive force that have
an absolute maximum value with respect to the other phase in each
one of said six time periods.
20. The method of claim 16, further comprising providing a spindle
motor for rotating said disk.
Description
FIELD OF THE INVENTION
[0001] The invention refers to a disk drive system and a method for
operating said disk drive system. Particularly said invention
refers to a hard disk drive system and a method for operating said
hard disk drive system.
BACKGROUND OF THE INVENTION
[0002] Contemporary hard disk drivers (HDD) typically include a
brushless DC motor within which a disk rotating spindle assembly
for rotating at least one data storage disk at a desirable
velocity, typically in a range between 5,000 and 10,000 revolutions
per minute, is provided. Storage disk devices such as a magnetic
disk devices etc. have been widely utilised as a storage devices of
a computer etc.
[0003] Hard disk drivers also typically include a rotary actuator
structure powered by a Voice Coil Motor (VCM). The rotary actuator
structure positions one or more transducer heads at desired
locations relative to surfaces of the disk or disks. More precisely
the VCM moves the head radially over the disk surface to thereby
enables the head to be positioned over any annular track on the
surface. In normal operation, the VCM, in response to control
signals coming from the computer, positions the transducer head
radially for recording data signals on or retrieving data signals
from a pre-selected one of a set of concentric recording tracks on
the disk.
[0004] The transducer head is supported above the disk surface by a
film of air to prevent contact therebetween which might thereby
otherwise damage one or both members. The head is typically
designed to actually fly above the disk recording surface of height
less than 50 microinches.
[0005] When the HDD is in power down condition the transducer head
must be placed on a parking zone to avoid any mechanical damages
determined by the contact between the head and the disk surface.
The parking zone may find on the central part of the disk surface
or outside the disk.
[0006] The placing of the head on the parking zone occurs even in
emergency condition, that is in condition of high temperature or in
presence of sudden knocks or when an electrical power failure slows
the disk, which allows the head to settle into contact with the
disk surface.
[0007] Generally all the modern disk drives incorporate means for
moving the head on the parking zone; this means is even activated
when the disk speed does not remain within tolerances, when a
positional error is detected or when write circuits faults that
could affect the stored data are detected.
[0008] A means for moving the head on the parking zone is disclosed
in U.S. Pat. No. 6,188,192 wherein a disk drive system is described
which includes a disk having a magnetic surface and supported for
rotation on a spindle, a magnetic head being movable relative to
the magnetic surface, and a spindle motor for driving the spindle.
The motor generates a back electromotive force voltage, so called
BEMF voltage, during an emergency condition and the system
comprises a plurality of switches for switching said BEMF voltage
and a plurality of comparators for comparing each phase of the BEMF
voltage. The system comprises a control circuit adapted to control
the plurality of switches to supply said BEMF voltage; the control
circuit comprises a decoder and a latch and provides to rectify
said BEMF voltage: This rectified BEMF voltage is supplied to the
VCM which directs said head to a stored position.
[0009] The above mentioned disk drive system however is complex and
presents high cost for its fabrication due above all to the use of
at least three comparators one for each phase of the BEMF
voltage.
SUMMARY OF THE INVENTION
[0010] In view of the state of the art described, it is an object
of the present invention to provide a disk drive system which
presents low fabrication cost.
[0011] According to the invention, such object is achieved by a
disk drive system including a disk having a magnetic surface and a
motor for rotating said disk, a magnetic head being movable
relative to said magnetic surface, said motor generating a back
electromotive force voltage having different phases, said system
comprising a plurality of switches for switching said back
electromotive force voltage, a control circuit to control said
plurality of switches to supply said back electromotive force
voltage to direct said head to a parking position, characterized by
comprising a comparator adapted to compare a single phase of the
back electromotive force voltage with the sum of the other phases
of said back electromotive force voltage, said comparator
generating an output signal representative of the comparation, said
system comprising a logic block controlled by the output signal of
the comparator and which is adapted to determine time periods and a
control sequence of the switches which is associated to said time
periods, said control sequence being supplied to the control
circuit so that the last generates control signals to control said
plurality of switches.
[0012] One method of operating a disk drive system in accordance
with the present invention involves a system which includes a disk
having a magnetic surface and a motor for rotating said disk and a
magnetic head movable relative to the magnetic surface. The method
involves the following steps: generating a back electromotive force
voltage having different phases; switching the back electromotive
force voltage by means of a plurality of switches; comparing a
single phase of the back electromotive force voltage with the sum
of the other phases of said back electromotive force voltage by
means of a comparator; determining time periods and a control
sequence of the switches associated to the time periods; generating
control signals to control the switches according to said control
sequence; and controlling the switches to supply the back
electromotive force voltage to direct said head to a parking
position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The features and the advantages of the present invention
will be made evident by the following detailed description of an
embodiment thereof which is illustrated as not limiting example in
the annexed drawings, wherein:
[0014] FIG. 1 shows a circuit scheme of a disk drive system
according to present invention;
[0015] FIG. 2 shows in more detail the block 3 in FIG. 1;
[0016] FIG. 3 shows the comparator belonging to the block 3 in FIG.
2;
[0017] FIG. 4 shows the logic circuit of the block 3 in FIG. 2;
[0018] FIG. 5 shows the three phases of the BEMF voltage generated
by the spindle motor in FIG. 1;
[0019] FIG. 6 shows a logic sequence associated to a time periods
which are determined by the logic circuit in FIG. 4.
DETAILED DESCRIPTION
[0020] As illustrated in FIG. 1, a spindle motor 1 is connected to
a three-phase H bridge power MOS 2 adapted to control said spindle
motor 1; said spindle motor is adapted to move a magnetic disk.
Said motor 1 is three phases motor comprising three phase voltage
generators Va, Vb and Vc connected with respective inductance La-Lc
in turn connected with respective resistors Ra-Rc. Controls signals
to control the operation of the motor 1 are input to the respective
gate terminals of the MOS transistors M1-M6 of the three-phase H
bridge power MOS 2. The transistor M3 is connected with the
transistor M4 to form a control circuit for a phase A of the motor
1; additionally the transistors M5 and M6 are connected together to
form a control circuit for a phase B of the motor 1 and the
transistors M1 and M2 are connected together to form a control
circuit for a phase C. The drain terminals of the transistor M1, M3
and M5 are connected together while the source terminals of the
transistors M2, M4 and M6 are connected together. A transistor M7
provide to connect the common line of the drain terminals of the
transistor M1, M3 and M5 with the supply voltage Vcc by means of a
voltage Vp normally applied at the gate terminals of the transistor
M7. However, in emergency condition or in power down condition, the
gate terminals of the transistor M7 is grounded by eliminating the
connection between the circuit 2 and the supply voltage Vcc. The
common line of the source terminals of the transistors M2, M4 and
M6 is connected to ground by means of a resistor R.
[0021] The VCM 10 is adapted to move a transducer head radially
over the surface of the disk and to place said head over any
annular track of the disk. A circuit 8 formed by a H-bridge of MOS
transistors M11-M14 is connected with the common line of the drain
terminals of the transistor M1, M3 and M5. The gate terminals of
the transistors M11-M14 are connected with a control circuit 11
adapted to drive the transistors M11-M14 in such a way that the
current flows in one path through the transistor M11, the VCM 10
and the transistor M13 or in another path through the transistor
M14, the VCM 10 and the transistor M12 to drive the VCM motor
either one way or another in accordance with the direction that the
head is desired to travel.
[0022] The block 3 includes a comparator circuit 4 and a logic
circuit 5, as illustrated in FIG. 2. The input terminals of the
comparator circuit 4 are connected with the phase A-C of the motor
1 while the logic circuit 5 has one input terminal connected with
the output terminal of the comparator circuit 4. The logic circuit
4 generates the output signals HA-HC and LA-LC which control
respectively the transistors M3, M5, M1 and M4, M6 and M2; more
precisely the logic circuit 5 generates the aforementioned signals
only in power down or in emergency condition.
[0023] The comparator circuit 4 is fabricated in such a way to
compare the sum of the two phases C and B and the phase A.
[0024] The comparator circuit 4 comprises three resistors R1, R2
and R3 connected respectively with the phases C, B and A at first
terminals. The resistors R1 and R2, which are equal value, are
connected to each other at the second common terminal connected in
turn with a gate terminal of a PMOS transistor M44, while the
resistor R3, which has a value equal to or different from that of
the resistor R1 or R2, has the second terminal connected with a
gate terminal of a PMOS transistor M43. The transistors M43 and M44
are the source terminals connected with each other and with a drain
terminal of a PMOS transistor M42 coupled in mirror configuration
with a PMOS transistor M41. The last mirrors the current flowing
through it and which flows through two NMOS transistors M45 and M46
which are connected in series between the drain terminal of the
transistor M41 and ground and are biased by means of respective
voltages VB1 and VB which find at gate terminals thereof. The drain
terminals of the transistors M43 and M44 are connected with
respective first terminals of resistors R4 and R5 the second
terminals of which are connected to ground; the drain terminals of
the transistors M41 and M42 are connected with the voltage Vcc. The
drain terminals of the transistors M43 and M44 are connected
respectively with the inverting and the non-inverting terminals of
a comparator 40 the output of which represents the output of the
comparator circuit 4. The output signal of the comparator 40 may
assume the values ground or Vdd.
[0025] The comparator circuit 4 is sensitive to the passage for the
zero voltage value of the phase A. In fact the comparator 40
changes the output value when the voltage of the phase A assumes
the zero value.
[0026] The BEMF voltage generates by the spindle motor 1 is shown
in FIG. 4. More precisely three phases of the of the BEMF voltage
are shown in FIG. 4, the phase A, the phase B and the phase C. The
phases A-C are sinusoidal voltages and in each period T1
corresponding to the evolution of 60 degrees of a phase, only two
of said three phases assume the maximum value, in absolute value,
with respect to the other phase. Therefore the transistors M1-M6
must be suitably driven in order to obtain the maximum voltage
variation on the VCM 10. A capacitor C provides to store the charge
by synchronous rectification of the spindle motor by properly
controlling the three half-bridges of the spindle motor.
[0027] For obtaining this result the logic circuit 5 comprises a
counter 51 which is activated when the output signal of the
comparator circuit 4 changes voltage value, more precisely when the
phase A assume a positive value, and which is deactivated when the
output signal of the comparator 40 changes newly voltage value.
Therefore the counter 51 counts the time period Ttot between a
value change and the successive value change of the output signal
of the comparator 40, that is the time period between one and a
successive zero crossing of the phase A; an external clock signal
CLOCK acts on the counter. A register 52, which is activated by the
same output signal of the comparator circuit 4, stores the period
time Ttot counted by the counter 51. A time divider 53 provides to
divide the time period Ttot by six time period T1 (which
corresponds to the evolution of 60 degrees of a phase) because, as
aforementioned, in each time period T1 two of three phases A, B and
C assume the maximum value in absolute value with respect to the
other phase. A logic device 54 associates to each time period T1
the turning on of two of the six transistors M1-M6 by means of two
of the control signals HA-HC and LA-LC according to a control
sequence defined in the table shown in FIG. 6. In said control
sequence the first time period T1 is divided by two (T1/2) because
the phases that have the maximum voltage value, in absolute value,
in this first time period T1/2 are the phases B and C and therefore
the transistor M5 and M2 must be turned on. In the second time
period T1 the phases that have the maximum voltage value, in
absolute value, are the phases A and C and therefore the transistor
M3 and M2 must be turned on. In the third time period T1 the phases
that have the maximum voltage value, in absolute value, are the
phases A and B and therefore the transistor M3 and M6 must be
turned on.
[0028] Said control sequence is supplied to a control device 55
adapted to generate the signals HA-HC and LA-LC to send to the gate
terminals of the transistors M1-M6. An external signal AT acts on
the control device 55 for allowing to send the signals HA-HC and
LA-LC only in power down condition or in emergency condition.
* * * * *